WMAgent: refactor pileup json location in the sandbox

[amaltaro]

Impact of the new feature
WMAgent

Is your feature request related to a problem? Please describe.
Disclaimer: meant to be a meta-issue!

This is not a core functionality for the partial pileup, but it would make the system more robust if we could actually decouple the pileup JSON dump from the workload sandbox tarball.

Currently, each pileup dump required by a workflow is created by WorkQueueManager and stored in two locations. First is in a directory tree such as:

cmst1@vocms0192:/data/srv/wmagent/current $ ls install/wmagentpy3/WorkQueueManager/cache/amaltaro_SC_6Steps_PU_Sept2023_Val_230907_205516_3876/WMSandbox/HIG_RunIISummer20UL16wmLHEGENAPV_03178_0/cmsRun3/
__init__.py  pileupconf.json  PSet.py

second is in the actual workflow tarball, which gets shipped to every single worker node as a condor TransferIn parameter, e.g.:

cmst1@vocms0192:/data/srv/wmagent/current $ vim install/wmagentpy3/WorkQueueManager/cache/amaltaro_SC_6Steps_PU_Sept2023_Val_230907_205516_3876/amaltaro_SC_6Steps_PU_Sept2023_Val_230907_205516_3876-Sandbox.tar.bz2 
WMSandbox/HIG_RunIISummer20UL16wmLHEGENAPV_03178_0/cmsRun3/pileupconf.json

Describe the solution you'd like
This ticket proposes many changes related to transferring and loading pileup information within the payload, such as:

• rename pileupconf.json to actually have an unique name based on a hash of the container name
• no longer ship the pileup information inside the sandbox tarball
• keep the new pileup information at the top level directory of a workflow cache (thus, in WMSandbox)
• compress all the relevant pileup configuration files and transfer it as an input to the job, hence as part of TransferIn in the SimpleCondorPlugin
• upon job bootstrap, uncompress the pileup tarball and leave its content at the job current directory
• update SetupCMSSWPSet to actually use a hash of the pileup name to find out which JSON file to load

A tricky question is, how do we know the pileup name at the SetupCMSSWPSet level? To be investigated

Describe alternatives you've considered
Keep transferring the pileup information within the workload tarball

Additional context
Related to #11537, but I don't think it should be a sub-task of.